1. Field of the Invention
This invention relates in general to a handheld electronic device, and more specifically to a handheld electronic device which has a cover unit and a base unit. The cover unit can slide smoothly and noiselessly on the base unit between open and closed positions.
2. Description of Related Art
Responding to a demand for making electronic devices lighter and thinner, electronic components have been developed with a tendency towards volume-miniaturization. Because the function of electronic components is more and more powerful and the volume thereof is more and more small, an electronic device of handheld type has been developed to replace electronic devices with a large size. The handheld electronic devices are for example, mobiles phone, PDAs (personal digital assistants) and handheld game consoles. In order to satisfy the demand of miniaturization, some handheld electronic devices are designed to have a sliding mechanism interconnecting a cover unit and a base unit whereby the cover unit can move relative to the base unit between an open position and a closed position. At the open position, an input unit, for example, a keypad of the handheld device is exposed. At the closed position, the keypad is covered by the cover unit. At the closed position, the handheld device has a reduced length whereby the handheld device can occupy a volume as small as possible.
Generally, for the above handheld device having a sliding mechanism, a display module is arranged on the cover unit, and a host system and a keypad are arranged in the base unit. A flexible printed circuit board is used to electrically connect the host system and the display module. The conventional sliding mechanism interconnecting the cover unit and the base unit of the electronic device, which is a structure of guide rail and guide slot, has drawbacks as follows.
The position of the guiding rail is not adjustable. If the position of the guiding rail is deviated from its intended position due to a deformation of the guiding rail during formation thereof by plastic injection molding, the cover unit and the base unit cannot have a precise fitting therebetween, resulting in that a smooth operation cannot be obtained when the cover unit is moved relative to the base unit.
Because the base unit and the cover unit are usually made of plastic material and the guiding rail and guiding slot are integrally formed therewith, the fit between the guide rail and the guide slot will be loose after repeat sliding movement between the cover unit and the base unit.
Because the guide rail and the guide slot have a linear contact which has a large friction, after repeat sliding movements between the cover unit and base unit, noise will be generated and the sliding between the guide rail and the guide slot will become not smooth.